数字和数字对象有什么区别？ [英] What is the difference between a number and a number object?

问题描述

存储在普通变量中的数字之间有什么区别：

What is the difference between a number stored in a normal variable:

var foo = 5; 

还有一个数字对象：

var bar = new Number(5);

我可以使用数字对象吗？

What can I use a number object for?

推荐答案

数字对象包含一些有用的方法和属性，例如：

A Number object contains some useful methods and properties such as:

Method                       Description
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
toExponential(x)    Converts a number into an exponential notation
toFixed(x)          Formats a number with x numbers of digits after the decimal point
toPrecision(x)      Formats a number to x length
toString()          Converts a Number object to a string
valueOf()           Returns the primitive value of a Number object

数字对象属性

Number Object Properties

Property                        Description
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
constructor         Returns the function that created the Number object's prototype
MAX_VALUE       Returns the largest number possible in JavaScript
MIN_VALUE           Returns the smallest number possible in JavaScript
NEGATIVE_INFINITY   Represents negative infinity (returned on overflow)
NaN             Represents a "Not-a-Number" value
POSITIVE_INFINITY   Represents infinity (returned on overflow)
prototype           Allows you to add properties and methods to an object

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